<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <input type="text">
    <script>
        var search=document.querySelector('input');
        document.addEventListener('keyup',function(e){
            if(e.keyCode===83){
                //focus搜索框获得焦点
                search.focus();
            }
        })
    </script>
</body>
</html>